Variable condenser



May 12, 1925. 1,537,561

F. E. STERN ET AL VARIABLE CONDENSER Filed Aug; 16 1922 Patented May 12, 1925.

UNITED STATES PATENT OFFICE.

FRANCIS E. STERN, OF WEST HARTFORD, AND J CLAYTON RANDALL, OF HARTFORD. CONNECTICUT, ASSIGNORS TO STERN & COMPANY, INCORPORATED, OF HARTFORD, CONNECTICUT, A. CORPORATION OF CONNECTICUT.

VARIABLE CONDENSER.

Application filed Augu t 16, 1922. Serial No. 582,124.

To all whom it may concern:

Be it known that we, FRANCIS E. STERN and J CLAYTON RANDALL, citizens of the United States, residing at lVest Hartford and Hartford, respectively, in the county of Hartford and State of Connecticut, have in vented a new and useful Improvement in Variable Condensers, of which the following is a specification. X

This invention relates to the type of condensers provided for radio communication sets that have a plurality of fixed plates and a plurality of plates interposed therewith and rotatively adjustable with relation thereto.

When the ordinary condensers of this character are in service and subject to the action of high frequency radio currents the movement of a body toward or from the condenser changes the static conditions. For instance, after the condenser is adjusted to give the best results the removal of the hand from the knob used to turn the movable plates will alter the capacity of the condenser sufliciently to throw the apparatus out of tune. Furthermore it is essential that the circuit connection with the movable plates be sure and positive under all conditions of service and wear, and that the movable plates be capable of easy movement when desired but that they be restrained from accidental movement after having been adjusted.

The object of the invention is to provide a simple, cheap and eflicient means which can be used as a guide for locating the con denser on the panel on which it is to be mounted and which means can subsequently be employed in such manner as to eliminate the objectionable influence of the movement of the body toward or from the condenser. Also to provide a tensioning means for the movable plates whichwill ensure a good and efiicient contact under all conditions of expansion, contraction and wear.

These objects are attained by forming an independent metallic disk With the necessary openings to enable it to be applied to the front of the panel to which the condenser is to be fastened and used as a templet for ensuring the exact drilling of the hole for the operating spindle and holes for the attachment screws through the panel, which disk is afterwards located on the front of the condenser between it and the back of the panel,

and grounded so as to neutralize the effect of the application of the hand to or the removal of the hand from the operating knob. And further by forming the tensioning spring that bears on the rear end of the spindle which carries the movable plates, in such manner that there is a line contact between the parts which keep bright and clean even under the wear of long and constant service.

In the accompanying drawings Figure 1 shows a top view of a condenser that enibodies the invention with the operating knob and dial, and the panel to which the device is attached, in section. Fig. 2 is a section on the plane of line 22 looking in the direction indicated by the arrows on Fig. 1. Fig. 3 is a back view of the condenser. Fig. 4: is a detail section on larger scale of the means attached to the back of the condenser frame for applying tension to the spindle which carries the movable plates.

The stationary plates 1, of which there may be any desired number, are substantially semi-circular pieces, preferably stamped from sheet aluminum. These plates properly spaced apart are fastened at their edges to three metallic rails 2 that are held between two semi-circular plates of insulation 3 by screws 4.

The movable plates 5 which alternate with the fixed plates are substantially semi-circular stampings preferably made from sheet aluminum. These movable plates properly spaced apart are attached at the middle to a spindle 6 which is mounted to turn freely in the insulating front and back plates of the frame. The front end of the spindle is eX- tended through the front insulating plate sufliciently to enable it to be passed through the panel 7 and be provided with the usual dial 8 and operating knob 9. At the rear the spindle extends through the back insulating plate and bearing upon this end, that is preferably rounded, is a leaf spring 10 which is fastened to the back plate by a screw 11. The free end of this spring is desirably cupped, and the cup provided with an opening 12 the edge of which bears upon the end of the spindle with a line contact. The; spindle is provided with a transverse stop pin 13 that is adapted to engage with '1" denser frame.

stop lugs 14 formed on the inside of the front insulating plate when the movable metallic plates are turned fully open or fully closed with relation to the fixed metallic plates.

The condenser is designed to be fastened to the back of the panel by screws 1 5 that pass through the panel into threaded holes in the front insulating plate, consequently the hole 16 for the spindle and the holes 17 for the attachment screws must be drilled or bored in the panel so as to exactly coincide with the corresponding'holes in the insulating front plate. Toensure the proper location of these holes in the panel a round metallic disk 19 is provided with a hole 20 that coincides axially with the spindle, and holes 21 that coincide with the screw holes in the insulating front plate of the con- This disk is preferably aluminum, and is first used as a templet on the front of the panel for locating the condenser and exactly centering the holes that are necessarily drilled, andthen when the condenser is attached to the back of the panel, the disk is placed between the front of the condenserand the back of the panel and grounded so as to act as a ground shield. This is possible because the spindle hole and the screw holes throughthe panel, the'disk which has been used as the templet, and the front insulating plate of the condenser frame, must coincide in view of the use of the metallic disk as a templet for these holes. Thus the disk provides exact templet usable for locating the holes also as an efficient shield which neutralizes the static conditions so that the movement of a body toward or from the front of the condenser will not affect the tuning of the apparatus.

The invention claimed is:

1. A variable condenser comprising fixed metallic plates, movable metallic plates interposed and rotatively adjustable between the fixed plates, means including a spindle for rotating the movable plates, a frame for supporting said plates and rotating means, said frame having attachment screw holes and a spindle hole, a supporting panel and a metallic static neutralizing disk of substantially the diameter of the condenser re- .movably held between the front of said frame and the back of the panel, said disk having a hole coinciding with said spindle and holes coinciding with the attachment screw holes in the frame, whereby said disk may be employed as a templet for locating the attachment screw holes in the panel.

2. A variable condenser compr'ising a supporting frame having insulating front and back plates and metallic rails connecting said plates, said front plate having a spindle hole and threaded screw holes, a plurality of semi-circular metallic plates attached to and supported by the rails, a spindle rotatively supported by the insulating plates, means for rotating the spindle, a plurality of semi-circular metallic plates attached to the spindle and rotatively adjustable between the fixed plates, and a circular metallic disk attached to the front plate, said disk having holes coinciding with the spindle hole and the screw holes in the 7 front insulating plate of the frame, whereby said metallic plate may be employed as a templet for locating the necessary holes in the supporting panel and subsequently be 'used as a neutralizing ground shield on the front of the condenser.

3. A variable condenser vcomprising a supporting frame having insulating front and back plates and metallic rails connecting said plates, a plurality of semi-circular metallic plates attached toand supported by the rails, a spindle supported by the insulating plates, means for rotating the spindle, a plurality of semi-circular metallic plates attached to the spindle and rotatively adjustable between the fixed plates, and a spring attached .to the back plate, said spring having a perforated end bearing upon the rear end of the spindle for making electrical contact therewith and applying tension thereto.

4. A variable condenser comprising a supporting frame having insulating front and back plates and metallic rails connecting said plates, a plurality of semi-circular metallic plates-attached to andsupportedby said rails, a spindle supported by the insulating plates, means for rotating the spindle, a plurality of semi-circular metallic plates attached to the spindle and rotatively adjustable between the fixed plates, and a spring attached to the back plate, said spring having a cup-shaped free end with an opening through the walls of the cup which bears with a line contact against the rear end of the spindle.

FRANOISE. STERN. J CLAYTON RANDALL. 

